Win98 cannot login to W2K Server

I just setup a new Win2K Server w/AD, all the WinXP Pro can login correctly,
but all the Win98, Win98 SE cannot, it shown “cannot find the user name”. I try to created a few new account for test and also cannot login. But I use the Win2K Server’s Administrator account can login correctly.
Could you tell me what wrong in this situation? Thanks.